Grinding mill



March 27, 1934- L. LEACH 1,952,322

GRINDING MILL Filed Nov. 17, 1930 3 Sheets-Sheet 1 FIG.I

March 27, 1934. L. LEACH 1,952,322

GRINDING MILL Filed Nov. 17, 19250 s Sheets-Sheet 2 INVENTOR m 1 ad BY 6% f-(MLMM ATTORNEY:

L. L. LEACH GRINDING MILL March 27, 1934.

Filed NOV. 17, 1930 3 Sheets-Sheet 3 FIG 5 WORNEYS I W Patented Mar. 27, 1934 UNITED STATES GRINDING MILL Lester L. Leach, Allentown, Pa., assig'nor to Fuller Lehigh Company, Fullerton, Pa., a corporation of Delaware Application November 17, 1930, Serial No. 496,072

3 Claims.

This invention relates to a grinding mill in which a synchronous motor is provided with a stator that is secured to the foundation of the mill and upon which the mill casing and other 5 parts may be supportedwhile the rotor of the motor is directly connected to a vertical driving shaft for the mill without any intermediate gearing. A thrust bearing is provided at the lower end of the driving shaft and another bearing is provided for the driving shaft in the base of the mill. The invention will be understood from the description in connection with the accompanying drawings in which Fig. 1 is a vertical section through an illustrative embodiment of the invention; Fig. 2 is a plan View of the mill; Fig. 3 is a section along the line 3-3 of Fig. 1; Fig. 4 is a section along the line 44 of Fig. 1 and Fig. 5 is a section along the line 5-5 of Fig. 1. In the drawings reference character 1 indicates a foundation for the mill which may be made of concrete. The foundation is provided with an annular ledge 2 to which the stator 3 of a synchronous motor may be bolted by means of the bolts 4.

A thrust bearing 5 is bolted to the central portion of the foundation by means of the bolts 6. Ventilating openings 7 and 8 may be provided for circulation of air through the foundation recess 1' below the motor.

A somewhat conically shaped base 9 of the grinding mill is supported upon the stator 3 with a series of supporting members 10 between the stator 3 and the base 9 of the mill.

A support 11 is provided on the base 9 for the lower grinding ring 12 and radially extending ports 13 are provided through the support 11. The casing 14 of the mill rests upon the support 11 and is provided with a cover 15 that may have a layer 16 of heat insulating material thereon. A cylindrical outlet 1'7 extends through the cover 15 and a cylindrical extension 18 is provided at the lower end of the outlet 17. The extension 18 is longitudinally adjustable by means of the bolts 19 that pass through the cover 15.

An air box 20 surrounds the lower portion of the casing 14 and rests upon the base 9. The air box is heat insulated by a layer of heat insulating material 20 at the inner side of its top, bottom, and outer side plates and the upper side thereof extends outwardly to form a platform around the mill. An inlet 21 extends into the air box 20 from a source of compressed air. Ventilating openings 7 are formed in the supporting members 10 to afford a circulation of air through the space between the motor and the mill base 9 carrying the air box 20.

A vertical driving shaft 22 is provided, the lower end of this shaft extending into the thrust bearing 5. The rotor 23 of the motor is attached to the shaft 22 and the motor has a sufficient number of poles to cause its speed to be suitable for efiicient grinding of the material in the mill. This material may be coal, for example. An upper bearing 24 for the shaft 22 is provided at the central portion of the base 9 of the mill. I

A lower row of grinding balls 25 rest upon the grinding ring 12 and a rotatable grinding ring 26 rests upon the balls 25. The ring 26 is provided with approximately radial ports 27 for air carrying ground particles to pass through. An upper row 28 of grinding balls rests upon the grinding ring 26 and an upper non-rotatable grinding ring 29 rests upon the balls 28. The ring 29 is provided with one or more lugs 30 that extend between lugs 31 along the inside of the casing 4 to prevent rotation of the ring 29, and permit vertical movement thereof. Compression springs 32 are provided for the grinding ring 29. These springs may bear upon the lugs 30. Adjustable rods 33 extend from the springs 32 through threaded bosses 34 on the cover 15, so that the compression of the springs 32 may be varied even while the mill is in operation.

By this invention the rotor 23 of the motor is connected directly to the shaft 22 without the interposition of any gearing or power transmission mechanism. The diameter of the rotor is considerably greater than the diameter of the' grinding rings 12, 26 or 29 or the diameter of the 9 rows of grinding balls 25 or 28, so that the tangential forces at the circumference of the rotor are increased at the grinding surfaces of the mill and the linear velocity of the grinding ring 26 is considerably less than that of the outer portion of the rotor.

The shaft 22 extends upwardly beyond the bearing 24 and a driving member 36 is connected to the extending portion of the shaft 22. This driving member 36 has a depending flange or skirt 37, the lower edge of which revolves in a groove provided therefor on the upper surface of the base 9. The member 36 drives the grinding ring 26 when the shaft. 22 is rotated with the lug 26' on the ring 26 in the socket 36 in the member 36, thus permitting relative vertical movement between the two. The flange 37 provides a wall along which the upwardly rising streams of air carrying the ground material pass.

A conical cover plate 38 is bolted to the grinding ring 26 so that as the shaft 22 revolves the plate 38 will be rotated. This cover plate prevents the material that is to be ground from collecting on the driving member 36 and feeds it to upper grinding balls.

An annular bafiie 39 extends around the'outside of the row of balls 28 and is vertically adjustable by means of rods 40 that pass through the cover 15.

A conical separator 41 is provided within the casing 14. The small end of the separator 41 extends downwardly and is left open, while the upper end extends above the lower end of the outlet 17. A conical air seal plate 41' is attached to the upper end of the shaft 22 just below the lower end of the separator 41 to prevent a current of air from entering this separator at the bottom. The separator 41 is adjustable by means of bolts 42 that extend through the cover 15.

Feed spouts 43 are provided to feed the material through the ring 29 on to the sloping surface of the cover plate 38 from which the material passes through the balls 28 and is ground to a certain extent. The partially ground material then passes by the bafiie 39 to the outside of the row of balls 25, thence through these balls where the material is further ground. The air passing from the air box 20 through the ports 13 picks up the ground particles as the streams of air rise along the outside surfaces of the skirt 37. The air carrying the ground particles passes out through the ports 27. The rotating ring 26 with ports 27 operates somewhat as a centrifugal fan to aid the movement of the air. The air then crosses the stream of falling particles from the baffle 39 where fine particles therefrom may be picked up and carried upwardly. The air and fine particles pass over the upper edge of the separator 41 and make a sharp turn under the extension 18, causing coarse particles to be separated and passed downwardly on to the surface of the cover plate 38 with the incoming material, while the air and fine particles pass out through the outlet 17.

In order to prevent dust from passing into the bearing 24 compressed air may be forced into this bearing through the pipe 44 from any convenient source. A labyrinth passage may be provided around the shaft 22 below the air inlet 44 so that the air will escape into the space Within the skirt or fiange 3'7 and prevent dust -or ground particles from finding their way into this space below the lower edge of the flange 37.

I claim:

1. An air swept grinding mill having a foundation, a synchronous motor having an annular stator supported on said foundation, an annular supporting structure mounted on said stator, a base member supported on and closing the upper side of said supporting structure, a mill casing of smaller diameter than said stator mounted on said base member, a rotatable grinding member in said casing, a thrust bearing, a vertical drive shaft mounted in said bearing and extending through said base member and operatively connected to said grinding member, a rotor for said motor directly mounted on said drive shaft, an annular air box having an outer casing mounted on said supporting structure and surrounding the lowermost part of said mill casing and discharging thereto, and ventilating openings formed in said supporting structure and communicating with., =the;=. space between said motor and said air box.

2. An air-swept grinding mill having a foundation with a recess in its upper side, a synchronous motor having an annular stator supported on said foundation, an annular supporting structure mounted on said stator, a conically shaped base member supported on and closing the upper side of said supporting structure, a cylindrical mill casing of smaller diameter than said stator mounted on said base member, a rotatable grinding member in said casing, a thrust bearing positioned in said foundation recess, a vertical drive shaft mounted in said bearing and extending through said base member and operatively connected to said grinding member, a rotor for said motor directly mounted on said drive shaft, an annular air box having an outer casing mounted on said supporting structure and surrounding the lowermost part of said mill casing and communicating therewith, and ventilating openings formed in said supporting structure and communicating with the space between said motor and said air box.

3. An air swept grinding mill having a foundation with a recess in its upper side, a synchronous motor having an annular stator supported on said foundation, an annular supporting structure mounted on said stator, a conically shaped base member supported on and closing the upper side of said supporting structure, a cylindrical mill casing of smaller diameter than said stator mounted on said base member, a rotatable grinding member in said casing, a thrust bearing in said foundation recess, a vertical drive shaft mounted in said bearing and extending through said base member and operatively connected to said grinding member, a rotor for said motor directly mounted on said drive shaft, an annular air box having an outer casing mounted on said supporting structure and surrounding the lowermost part of said mill casing and communicating therewith, ventilating openings formed in said supporting structure and communicating with the space between said motor and said air box, heat insulating material on the bottom plate of said air box, and the top plate of said air box being arranged to form an annular platform around the upper part of said mill casing.

LESTER L. LEACH. 

